Experimental Neutron Damage Equivalences Utilizing Device Parameters

When considering neutron-induced damage to transistors, it is desirable to relate the damage caused by one spectrum to that of another. Recent experimental work shows that the damage curves based on displacements in bulk silicon are an over simplification when applied to devices, and give significant errors. Using the experimental technique described in this paper, it is possible to compare the damage of different spectra using the actual device parameter of prime interest. Results obtained using this technique show that damage induced in devices involves several damage mechanisms and is more complex and severe than that predicted from displacements alone. While damage ratios for different spectra may be quantitatively obtained, a totally satisfactory explanation for the increasing damage for spectra becoming increatingly "harder" is not presently available. The difficulty of explaining the damage ratios obtained that are larger than anticipated is compounded by the fact that these ratios appear to be dependent upon the operating point of the device, the device parameter used as a basis, and possibly the device type.